Investigation on microstructure and mechanical properties of reactively synthesized TiAlN/AlON nanomultilayers

Abstract

The novel TiAlN/AlON nanomultilayers with different AlON layer thickness were synthesized by reactive magnetron sputtering. The microstructure and mechanical properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM) and nano-indentation techniques. The results indicated that, under the template effect of fcc (face-centered cubic) TiAlN layers, originally amorphous AlON layers were crystallized and grew epitaxially with TiAlN layers when AlON layer thickness was below 0.7nm. Accordingly, the hardness and elastic modulus of the nanomultilayers increase and reach the maximum values of 36.2 and 385.6GPa, respectively. With further increase of AlON layer thickness, AlON layers transformed back into amorphous state and broken the coherent growth of nanomultilayers, leading to the decrease of hardness and elastic modulus. The strengthening mechanism of TiAlN/AlON nanomultilayers was further discussed.